Since the author of the referenced article (Ephraim Rubin) has so far
not replied to Norowitz's question, I'll try to do so instead. As
indicated in Rubin's article, the information about Streicher having
shouted "Purim 1946" right before he was hanged comes from New York
Times. I don't believe that there is any other source of that
information, which originated with the witnesses of Streicher's
execution (there was reportedly a group of witnesses representing the
press and judicial officials from the allies). As to why Streicher
shouted that phrase, it seems that the only one interpretation is that
he alluded to the analogy between hanging of Haman's ten sons reported
in Esther, and hanging of the Nazi bunch, which in Streicher's
anti-Semitic mind was in both cases allegedly done solely on behalf of
Jews.